2017-04-28 04:38:10

by Mika Penttilä

Subject: nvdimm/pmem device lifetime

Hi,

Just wondering the pmem struct device vs gendisk lifetimes.. from pmem_attach_disk():

device_add_disk(dev, disk);
devm_add_action_or_reset(dev, pmem_release_disk, disk);


where:
static void pmem_release_disk(void *disk)
{
del_gendisk(disk);
put_disk(disk);
}


but device_add_disk() makes disk pin dev (as a parent), and it's unpinned by del_gendisk()
which is called when dev is released, but it's not because of this circular dependency?

--Mika

2017-04-28 15:36:56

by Dan Williams

Subject: Re: nvdimm/pmem device lifetime

On Thu, Apr 27, 2017 at 9:37 PM, Mika Penttilä
<[email protected]> wrote:
> Hi,
>
> Just wondering the pmem struct device vs gendisk lifetimes.. from pmem_attach_disk():
>
> device_add_disk(dev, disk);
> devm_add_action_or_reset(dev, pmem_release_disk, disk);
>
>
> where:
> static void pmem_release_disk(void *disk)
> {
> del_gendisk(disk);
> put_disk(disk);
> }
>
>
> but device_add_disk() makes disk pin dev (as a parent), and it's unpinned by del_gendisk()
> which is called when dev is released, but it's not because of this circular dependency?

pmem_release_disk() is called when the driver is unbound, well before
the device is released. See the calls to devres_release_all() in the
device_release_driver() path.